A technology for compensating a harmonic current by using an active filter and thereby suppressing harmonics is introduced, for example, in Japanese Patent No. 4411845, Japanese Patent No. 4284053, and Japanese Patent Application Laid-Open No. 2005-223999.
In Japanese Patent No. 4411845, a DC voltage, which is boosted by a boost chopper and is given to a smoothing capacitor, is directly applied to an active filter.
In Japanese Patent No. 4284053, a DC voltage, which is obtained by rectifying an AC voltage boosted by a transformer and is given to a DC smoothing capacitor, is directly applied to an active filter as a voltage type self-excited power converter.
In Japanese Patent Application Laid-Open No. 2005-223999, an inverter-side capacitor is disposed between a transformer and an inverter, and is connected in parallel to a rectifier-side capacitor via one protection diode.
In Japanese Patent Application Laid-Open No. 2002-51589, a so-called electrolytic capacitor-less inverter is disclosed.